There is a need for reagents, kits and methods for screening, diagnosing and monitoring individuals with cancer originating from the alimentary canal, particularly primary and metastatic stomach and esophageal cancer and metastatic colorectal cancer. There is a need for reagents, kits and methods for identifying and confirming that a cancer of unknown origin is originating from the alimentary canal and for analyzing tissue and cancer samples to identify and confirm cancer originating from the alimentary canal and to determine the level of migration of such cancer cells. There is a need for compositions which can specifically target colorectal, stomach and esophageal cancer cells. There is a need for imaging agents which can specifically bind to colorectal, stomach and esophageal cancer cells. There is a need for improved methods of imaging colorectal, stomach and esophageal cancer cells. There is a need for therapeutic agents which can specifically bind to colorectal, stomach and esophageal cancer cells. There is a need for improved method of treating individuals who are suspected of suffering from primary and/or metastatic stomach or esophageal cancer or metastatic colorectal cancer. There is a need for vaccine composition to treat colorectal, stomach and esophageal cancer. There is a need for vaccine composition to treat and prevent metastasized colorectal, stomach and esophageal cancer. There is a need for therapeutic agents which can specifically deliver gene therapeutics, antisense compounds and other drugs to colorectal, stomach and esophageal cancer cells.